1. Field of the Invention
The present invention relates to a method for controlling a data transfer buffer suitable for use when capacity of the buffer is limited in a computer system in which information is transmitted and received through the buffer.
2. Description of the Prior Art
In a computer system, a memory area called a user space is allocated to each of a plurality of user programs in a main memory.
When data is to be transferred between user spaces transfer data is stored under control of the user program, from a transferring location, to a transfer buffer in a memory area to be commonly accessed by the user programs, and the data in the transfer buffer is received, under control of a user program from a destination location, by a memory area to which the user program of the destination area belongs. In the prior art system, sufficient consideration was not paid to the capability of reception at the destination space, and the transfer data would be stored in the transfer buffer area in response to a transfer request irrespective of whether the destination space is ready to receive the data or not. The information is enqueued to a transfer querie which manages readout of the stored data. As a result, if the destination station is not ready to receive the information, the information is held in the transfer buffer area. Thus, if a large amount of data is transferred between spaces, the information may be held for a long time. JP-A-58-1222 teaches providing a large capacity data buffer and sharing it for a plurality of times of data transfer.
However, even in this above manner, there is a certain probability that most portions of the buffer area may be occupied by data. In this case, the request for data transfer is rejected.